Dressing for attention, especially to get the attention of the opposite or same sex; however, in a subtle way that is congruent to the identity you are projecting. In addition, 'peacockin' involves not being rattled by social pressure.

For example, an unconfident nerd wearing a New Era hat and perhaps a scarf and is obviously self-conscious and or lets others comments on his attire alter his behavior/attitude is not exhibiting 'peacock swag.'